Software defined networking (SDN) is networking in which the configuration of a network, paths for each service, or the like may be dynamically set and changed. In SDN, an SDN controller sets up a plurality of SDN switches. Among the plurality of SDN switches, a network for data transmission is constructed. Between the plurality of SDN switches and the SDN controller, a network for control is constructed so as to be physically or logically separate from the network for data transmission.
FIG. 1 is a diagram illustrating an example of processing upon occurrence of a failure in an SDN network. In the SDN network illustrated in FIG. 1, an OpenFlow interface is used. Physical devices, fibers, and the like are shared among SDN switches. In the case where a sudden failure such as a device failure or a fiber disconnection occurs, an SDN switch, having detected link disconnection due to this failure, sends to the SDN controller a Port Status message that notifies the SDN controller that link disconnection has occurred.
Upon receiving the Port Status message from the SDN switch, the SDN controller performs routing for each service that performs communication over a route passing through the port of which the SDN controller has been notified by the Port Status message. Once a new route is decided by routing, a Flow Mod message from the SDN controller notifies each SDN switch to set the new route. The SDN switch stores a flow table in which behaviors of each service for packets are defined. The SDN switch records setting of the new route in the flow table according to the Flow Mod message. From that point on, the SDN switch transfers packets using the new route according to the flow table. As related art techniques, for example, Japanese Laid-open Patent Publication No. 2007-49336 and Japanese National Publication of International Patent Application 2006-503506 are disclosed.
However, when many services for which routing is to be performed are present, the processing load on the SDN controller caused by routing increases, and thus there is a possibility that processing congestion will occur in the SDN controller. If processing congestion of the SDN controller occurs, the time taken until a new route is decided becomes longer. In this case, in an SDN switch having a port where a failure has occurred, there is a possibility that a large number of received packets will be discarded.
When processing congestion of the SDN controller or packet discarding occurs, communication might be cut off for a long time in the service in question.
When the SDN switch receives an unknown packet, information on which is not found in the flow table, and sends a Packet In message to the SDN controller, there is also a possibility that a phenomenon where communication is cut off for a long time will occur. The SDN controller, upon receiving the Packet In message, performs a routing process for the unknown packet of which the SDN controller has been notified by the received Packet In message. It is desirable to be able to reduce the time over which communication is cut off as a result of the occurrence of processing congestion due to reception of routing requests of an information processing device that performs routing.